1. Field of the Invention
The present invention relates to the catalytic conversion of H.sub.2 S and SO.sub.2 mixtures into free sulfur. More specifically, it is concerned with the efficient removal of sulfur from a relatively low H.sub.2 S-containing gas stream, e.g., 45 mole percent or less, containing hydrocarbon or other contaminants which are harmful to the Claus catalyst, being accomplished in a so-called straight-through Claus-type catalytic sulfur recovery process wherein additional fuel gas is used to maintain adequate combustion temperature in the combustion furnace. In particular, it deals with an improved method of utilizing excess heat of combustion produced in the straight-through furnace to reduce the amount of additional fuel gas consumed, thus leading to a more energy efficient process.
In the process disclosed in U.S. Pat. No. 3,860,697 an acid gas containing less than 45 mole percent H.sub.2 is processed through a straight-through-type furnace wherein the proper furnace temperature and flame stability is achieved by adding supplementary fuel gas with or without a portion of the acid gas stream along with the air or oxygen to a first combustion zone which is then followed by a second combustion zone which processes all of the acid gas stream. The present invention is specifically related to this process and is viewed as an improvement thereof. As such, the enabling disclosure aspects of U.S. Pat. No. 3,860,697 are here incorporated by reference.